BAGHDAD, Iraq - U.S. troops backed by helicopter gunships battled with insurgents overnight near the southern holy Shiite city of Najaf, killing 43 gunmen and destroying an anti-aircraft system belonging to the insurgents, the U.S. military in Baghdad said today.

The fighting began Monday night and lasted several hours, a military spokesman said. It came as around 200 U.S. forces made their first deployment inside Najaf, moving into a base that Spanish troops are vacating about three miles from holy shrines near where an anti-American Shiite Muslim cleric is holed up.

Night footage taken by the Associated Press Television News, from a road between Najaf and the nearby town of Kufa, showed U.S. army helicopters flying low over plumes of smoke rising from a green area and the sparks of flashes, likely from gunfire.

U.S. commanders have said they will not move against the shrines in order to capture cleric Muqtada al-Sadr, whose armed supporters have launched attacks against the U.S.-led forces.

Attempts to capture al-Sadr have been put on hold while negotiators try to resolve the standoff. The Americans say they're aware that moving against the shrines could turn the cleric's limited revolt into a wider anti-U.S. uprising by Iraq's Shiite majority.

The military didn't give any more details of the fighting, besides saying 43 insurgents were killed and ant-aircraft system destroyed.

Earlier Monday, U.S. troops came under a heavy insurgent attack in Fallujah a day after U.S. officials decided to extend a cease-fire rather than launch a full-scale offensive on that city. Eight suspected insurgents and one U.S. Marine were killed.

U.S. Marines battled Sunni guerrillas around a mosque in Fallujah's Jolan district, a poor neighborhood where insurgents are concentrated. U.S. helicopter gunships joined the battle. Tank fire demolished a minaret from which U.S. officials said gunmen were firing.

The U.S. troops met "a real nasty bunch," said Lt. Col. Brennan Byrne, commander of the U.S. military's 1st Battalion, 5th Marine Regiment. But he said the violence would not deter plans to begin joint U.S.-Iraq patrols.

The patrols are a key part of the U.S. effort to establish a semblance of control over Fallujah without a wider assault, which would revive the bloody warfare seen earlier this month. The United States decided to try the patrols after President Bush consulted with his commanders over the weekend, and the cease-fire was extended in part to allow for patrols to be organized.

The fighting in Fallujah was the latest violence to shake a two-week-old cease-fire. Still, U.S. officials said they wanted to press forward with a political track, a day after abruptly toning down threats to launch a full-out assault on the city.

"We will take the time necessary to see if there is not a political solution," Secretary of State Colin Powell said Monday. "But as you saw today, when our soldiers and our Marines are attacked, they will respond and they will respond with force to protect themselves."